The present invention relates to stormwater sedimentation, separation, filtration and treatment systems and a method of stormwater sedimentation, separation, filtration and treatment. More specifically the present invention relates to an above grade canister type filtration system utilizing replaceable filter cartridges within the canisters combined with an electronic control system and automatic valve, a floating separation device, and a method of filtering stormwater runoff from developed areas.
In recent years, many local state and federal regulations have required installation of stormwater abatement systems to achieve filtration of stormwater runoff prior to exiting development projects. Many developments are required to construct and maintain stormwater sedimentation and filtration basins with each basin having a particular configuration to match the particular development project. However, existing basins have been constructed with the primary purpose of capturing and filtering prior to the release of a certain quantity of stormwater runoff from the development project. The majority of the current stormwater filtration sedimentation basins utilize a sand filter bed usually eighteen inches or more in depth overlying along or beneath the grade perforated polyvinyl chloride (PVC) pipe or the like. This current method is designed to cause the stormwater captured in the basin to be drained by gravity through the sand bed causing filtration of the water prior to entering the PVC drain pipes beneath the sand filtration media.
The current technology utilized in existing sedimentation and filtration basins has a variety of problems. The primary problems associated with the current technology are that small particulate matter in the stormwater settles to the bottom of the filtration basin causing a blinding and clogging of the filter media (i.e., sand), unacceptable draw-down, point discharging, water stagnation, and increased bypass potential. To overcome these problems the party responsible for maintaining the stormwater filtration system must incur enormous costs in regrading, raking, and often times replacing the filter media (i.e., sand, or diatomaceous earth, etc.) after each rainfall event.
A further problem is the large amount of land required for construction of a sedimentation basin and a separate filtration basin used in combination for stormwater control. By combining the sedimentation and filtration processes within the same basin, the amount of land needed for the entire stormwater filtration system (basins, etc.) is dramatically reduced affording the developer additional developmental land or reducing the overall land required to be purchased for a development project.
Yet a further problem is the disposal of large quantities of filter material (i.e., sand, diatomaceous earth, etc.) during maintenance. When the filter media becomes contaminated, polluted or otherwise inefficient or ineffective, the filter media has to be physically removed and transported off-site for disposal. In almost every case the quantity of filter material currently being removed and transported for disposal drastically increases the cost of maintenance. Additionally, with current technology a responsible party cannot perform maintenance on or dispose or replace filtration media at times when the media has become clogged or blinded and the basin above the media is full of stormwater runoff. The present invention provides for a contained cartridge type filtration system which can be installed above grade in a horizontal or vertical position which will allow gravity filtration of stormwater at appropriate times through canister filtration systems utilizing filter media which can be easily removed and disposed in on-site disposal containers or through other appropriate means. It provides a filtration system which allows for filter media replacement with water standing in the filtration and sedimentation basins without causing the risk of release of contaminated stormwater.
Although there have been devices that either filter stormwater or devices that cause the shut off of stormwater flow upon the sensing of pollution, the present invention utilizes a distinct and unique technology involving a process and mechanism of combined sedimentation, separation and filtration. Automated sensing and logic components provide filtration at an optimum level; together with a mechanism to prevent water flow until maximum filtration and maximum sedimentation have been achieved. This multi-function device and process is distinguishable from the prior art with respect to both the filtration of stormwater as well as the shut off of stormwater flow upon sensing pollutants. While existing devices provide for a removable filtration medium, they all have a common element of being at or below grade. The present invention provides an above grade filtration canister system, not activated until maximum sedimentaiton and separation has occurred, and filtration of the "first flush" of runoff water having the heaviest concentration of pollutant loadings. The runoff which occurs after the "first flush" has been captured is diverted into the stormwater sewer system. The entire "first flush" runoff contemplated in this process is contained in a basin to allow maximum filtration, separation and sedimentation prior to it being treated through the filters with subsequent release through automatic shut off valve into a collecting stormwater sewer system or receiving stream.